Nitrogen-induced changes in colony density and spore production of Erysiphe graminis f.sp. hordei on seedlings of six spring barley cultivars

Abstract

The influence of increasing nitrogen supply (30, 60, 120 and 240 mg N per pot) oil susceptibility was studied on seedlings of six cultivars of spring barley inoculated with virulent isolates of powdery mildew. The colony density (CD) measured as colonies per cm2 was significantly increased with increasing application of nitrogen on all cultivars, and a significant interaction was found between N and cultivar. The different reactions of the cultivars could not be ascribed to lack of N uptake. In general, increasing N application enhanced the sporulation capacity of colonies (CSC) irrespective of increased CD and the cumulative production of spores per cm2 leaf (CSCM) increased strongly with N application in all cultivars. No interaction between N and cultivar was found for the latter component. The increase in CSCM closely corresponded with the increase in N content and fresh weight of uninoculated leaves. No interaction between N treatment and powdery mildew isolates was found for infection efficiency and spore production per colony, when tested on one cultivar. The N-induced changes in infection and sperulation can explain the main part of the increasing effect of N fertilization on powdery mildew development on the field. The results indicate that it may be possible to breed for or select barley cultivars with low N impact action on powdery mildew development.